Question

I wrote this piece of code and I can’t figure out what I exactly did wrong. I create two instances of the ‘Route’ class, and somehow they share the value for the ‘coords’ list.

import random

class Route():
    def __init__(self):
        self.coords = []  
        self.distance = 0
    def Generate(self, cities):
        random.shuffle(cities)
        self.coords = cities

class Citymap():
    def __init__(self, nr):
        self.Nr_of_cities = nr
        self.cities = []
    def Generate_map(self):
        for i in range(0, self.Nr_of_cities):
            self.cities.append((random.randint(0, 750), random.randint(0, 750)))


city = Citymap(6)
city.Generate_map()

a = Route()
a.Generate(city.cities)

b = Route()
b.Generate(city.cities)

print a.coords
print b.coords

The output of a and b:

[(429, 713), (336, 611), (555, 465), (397, 227), (222, 412), (491, 322)]
[(429, 713), (336, 611), (555, 465), (397, 227), (222, 412), (491, 322)]

a and b should be different instances but somehow they end up sharing the ‘coords’ variable. Could someone help me out?

Answer 1

You have to clone the city.cities list or it will just be shared between them :

a = Route()
a.Generate(city.cities[:])

b = Route()
b.Generate(city.cities[:])